1. Technical Field
Embodiments of the invention relate generally to power electronics. Other embodiments relate to detecting a shorted diode or other electronic component in an alternator rectifier.
2. Discussion of Art
Generally, electric vehicles develop tractive effort through motors fitted to axles or wheel hubs of the vehicles. These motors receive electrical power from a primary power supply, which may be an electrochemical battery, an ultracapacitor, a photovoltaic panel, or a thermochemical engine. If the primary power supply is a thermochemical engine, it is typical for motion of the engine to drive an alternator (AC generator), which rotates at a multiple of the engine cycle rate. In order to provide a clean source of power regardless of engine speed, the electricity generated in the alternator is passed through an alternator rectifier, and possibly additional power electronics, before delivery to the motors. Nevertheless, rotation of the alternator unavoidably introduces a small AC ripple to the electrical power delivered from the alternator rectifier.
Typically, the alternator rectifier is a solid state device, although it also can be built from discrete components. In any case, if a diode of the alternator rectifier fails short (zero resistance), a large or extremely large AC fault current may flow down to other power electronics, so that continued operation can present a risk of secondary damage to the power electronics as well as to the motors.
Accordingly, some electric vehicles provide for an emergency mode of operation of the vehicle in case of an alternator rectifier diode fault. Also, some electric vehicles automatically enter the emergency mode in response to detecting an alternator rectifier diode fault.
Typically, alternator rectifier diode faults have been detected on the basis of an abrupt or gradual increase in the magnitude of AC ripple in the electrical power delivered from the alternator rectifier. However, to avoid nuisance (false fault) detections, diode fault detection has been disabled for normal operation transients such as motor/alternator (regenerative braking) transition, wheel slip, speed transients, power regulation mode changes, etc. These customary exclusions from fault detection produce the predictable problem that there is a possibility of not detecting an alternator rectifier diode short during normal operations.
In view of the above, it may be desirable to provide apparatus and methods for reliably detecting an alternator rectifier diode short during any normal operations of an electric vehicle, including transients for which diode fault detection previously has been disabled. Such apparatus and methods might also be helpful toward detecting any alternator rectifier diode short fault.